R: Download image using rvest

问题:

I'm attempting to download a png image from a secure site through R.

To access the secure site I used Rvest which worked well.

So far I've extracted the URL for the png image.

How can I download the image of this link using rvest?

Functions outside of the rvest function return errors due to not having permission.

Current attempts

library(rvest)
uastring <- "Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36"
session <- html_session("https://url.png", user_agent(uastring))
form <- html_form(session)[[1]]
form <- set_values(form, username = "***", password="***", cookie_checkbox= TRUE)
session<-submit_form(session, form)
session2<-jump_to(session, "https://url.png")

## Status 200 using rvest, sucessfully accsessed page.    
session 
<session> https://url.png
  Status: 200
  Type:   image/png
  Size:   438935

## Using download.file returns status 403, page unable to open.
download.file("https://url.png", destfile = "t.png")
    cannot open: HTTP status was '403 Forbidden'

Have tried readPNG and download.file on the url, both of which failed due to not having permission to download from a authenticated secure site (error: 403), hence why I used rvest in the first place.

回答1:

Here's one example to download the R logo into the current directory.

library(rvest)
url <- "https://www.r-project.org"
imgsrc <- read_html(url) %>%
  html_node(xpath = '//*/img') %>%
  html_attr('src')
imgsrc
# [1] "/Rlogo.png"

# side-effect!
download.file(paste0(url, imgsrc), destfile = basename(imgsrc))

EDIT

Since authentication is involved, Austin's suggestion of using a session is certainly required. Try this:

library(rvest)
library(httr)
sess <- html_session(url)
imgsrc <- sess %>%
  read_html() %>%
  html_node(xpath = '//*/img') %>%
  html_attr('src')
img <- jump_to(sess, paste0(url, imgsrc))

# side-effect!
writeBin(img$response$content, basename(imgsrc))

回答2:

Try this example below:

library(rvest); library(dplyr)

url <- "http://www.calacademy.org/explore-science/new-discoveries-an-alaskan-butterfly-a-spider-physicist-and-more"
webpage <- html_session(url)
link.titles <- webpage %>% html_nodes("img")

img.url <- link.titles[13] %>% html_attr("src")

download.file(img.url, "test.jpg", mode = "wb")

You now have "test.jpg" which is the picture:

Hope this helps!